1. Field of the Invention
This invention relates to inhalers, i.e., those devices for administering, by inhalation, medicaments in finely divided form contained in capsules.
2. Description of Related Art
In particular, reference should be made to the inhaler described in U.S. Pat. No. 4,069,819, one of the two inventors of which is also one of the two inventors of the present invention. Said patent describes an inhaler of overall cylindrical shape comprising a body enclosing an axially extending nebulization chamber. A capsule containing the medicament in finely divided form is placed in the chamber. The capsules of this type have an overall cylindrical shape with their two ends each having the shape of a spherical cap. The nebulization chamber is of overall cylindrical shape and has a substantially larger cross-section than the cross-section of the capsule to be placed in the chamber. This latter communicates with the outside through air inlet apertures in the chamber wall at or in proximity to one end of the chamber and shaped to generate a swirling air flow through the chamber during inhalation. The chamber also communicates with the outside through air discharge apertures provided in the other spherical cap-shaped end of the chamber and opening into an axial discharge duct. The inhaler is also provided with a piercing device for piercing the casing of the capsule which has previously been inserted into the nebulization chamber. The piercing device is arranged to produce two or more holes in that spherical cap-shaped end of the capsule facing the air inlet apertures.
When the capsule has been pierced, the user brings inhaler up to his nostril or mouth and breathes in. On breathing in, the particular arrangement of the air inlet holes generates within the nebulization chamber a swirling air flow which causes the pierced capsule to undergo such movements as to cause the medicament in finely divided form to escape through its holes, so that the powder is entrained outwards by said air flow. The powder passes through said discharge apertures and flows along the subsequent discharge duct until it reaches either the oral cavity or the nasal cavity of the patient, as the case may be.
However, the aforesaid inhaler has certain drawbacks. In this respect it has been found that in a large number of cases the emptying of the capsule is irregular and incomplete, with consequent difficulties in administering the finely divided medicament.
This drawback is obviated by the invention described in the patent application entitled INHALER WITH REGULAR COMPLETE EMPTYING OF THE CAPSULE in the name of the proprietor of the present patent application and filed on the same date as the present application (i.e., now U.S. Pat. No. 4,995,385). It describes how the nebulization chamber has to be constructed to ensure emptying of the capsule containing the medicament in finely divided form. Specifically, said patent application describes by way of example an embodiment of a disposable inhaler, into which the capsule is inserted during the assembly of the various component pieces of the inhaler. A piercing device enables the capsule to be pierced on use.
An examination of the drawings of said patent application, which illustrate the said disposable inhaler, shows that it is still of rather complex structure as it has to also comprise said capsule piercing device.